The objective of this study is to determine if elastic support stockings will significantly reduce the degree to which cardiac output decreases when pregnant women stand. In addition, support stockings may significantly reduce the frequency of uterine activity which follows the change from the supine to standing position. Pregnant women are tested without support stockings, asked to wear the support stockings during all waking hours for one week, and then retested. To date, approximately 1/4 of the anticipated 40 participants have been studied. Recruitment for this project has proven difficult but we will attempt to enroll the balance of the study population in the coming year.